Commercial and consumer refrigerators do an excellent job of maintaining a refrigerated storage space at a cold temperature, providing the refrigerator access door is not left open too long. When the refrigerator door is closed, the refrigerated storage space is essentially hermetically sealed from ambient air. Under these conditions, the refrigeration mechanism can maintain the storage space at a desired low temperature.
However, if the door is left open too long, foodstuffs within the storage space can spoil. Further, the refrigeration mechanism itself can be damaged as it attempts to restore a cold temperature to a storage space that is now exposed to warmer ambient air.
Several devices are known in the art to alert a user that the door to a refrigerator is ajar or completely open. U.S. Pat. No. 2,302,072 (1939) to Tickell discloses a portable battery operated flashlight-like device that is placed inside a refrigerator storage space. A thermostat associated with the device senses storage space temperature and causes a light (or an audible alarm) in the device to turn on when the temperature becomes too high. Unfortunately Tickell's device is rendered useless when the batteries fail.
U.S. Pat. No. 5,451,930 (1995) to McDaniel discloses a rather more sophisticated device that senses both a door ajar condition and a too high refrigerator temperature, and can activate at least one alarm when either condition is sensed. Unfortunately McDaniel's device is relatively expensive to produce and requires professional installation because it requires tapping into electrical switches within the refrigerator. While McDaniel's device might be incorporated into a new refrigerator during manufacture (assuming one could justify the device cost), the device is not readily retrofittably attached to an existing refrigerator, especially by a layperson.
In summary, while door ajar detection devices are known, the devices typically require batteries and are not failsafe (e.g., Tickell '072), or are expensive and cannot readily be installed by a layperson in an existing refrigerator. Thus, there is a need for a door ajar detector that does not require batteries, is inexpensive to fabricate, and can be retrofitted to an existing refrigerator by a layperson. Preferably such device should optionally signal when refrigerator temperature has become too high.
The present invention provides such a device.